Aquaculture CRSP 21st Annual Technical Report
Broodstock Diets and Spawning of Colossoma macropomum and/or Piaractus brachypomus
Tenth Work Plan, Feeds and Fertilizer Research 2 (10FFR2A)
University of Arkansas at Pine Bluff
Pine Bluff, Arkansas, USA
The overall objective of this study was to determine the effect of improved broodstock nutrition on maturation and spawning performance of gamitano (Colossoma macropomum) and/or paco (Piaractus brachypomus). In October 2002, ovules, semen, and plasma samples from gamitana and paco broodstock fed diets containing 30 or 40% protein were collected for laboratory analysis. The samples were stored frozen at Instituto de Investigaciones de la Amazonia peruana (IIAP) until they were transported to University of Arkansas at Pine Bluff (UAPB) in 2003. Total lipids, lipid class composition and fatty acid composition were analyzed for the tissues from paco and gamitano. However, statistical analysis to determine diet effects could only be performed on the plasma samples because insufficient ovule and semen samples were available. Calculated amino acid and fatty acid composition of the diets based on literature values and unpublished data is presented. The energy:protein (E:P) ratios in the diets for this study were still low, despite the addition of palm oil to both diets. The n-3 fatty acid levels and the n-3:n-6 ratios were also low in both diets relative to published recommendations for reproduction. There was no effect of diet on the total lipid, lipid classes or fatty acids in plasma of either gamitano or paco. Specific fatty acids such as arachidonic acid (20:4n-6), eicosapentaenoic acid (20:5n-3) and docosahexaenoic acid (22:6n-3) that are important in reproduction in other fish species were present in much higher amounts in the tissues (plasma, ovules, and semen) than in the diets. Because freshwater fish can synthesize some of the long-chain highly unsaturated fatty acids from precursors the identification of lipid sources that will enhance reproduction in characids requires additional research.
Nutrition is known to affect reproductive success in fishes (De Silva and Anderson, 1995), but the effects are not well documented in characids. Past spawning failures of captive characids in Iquitos could be due partly to poor nutrition. The diet used in WP9 to maintain broodstock in Iquitos contained about 32% protein, which is intermediate between the requirements for larval and adult characids (Araujo-Lima and Goulding, 1997). However, the diet appeared to contain a suboptimal amount of total energy compared to diets used in most feeding experiments with characids. Insufficient levels of non-protein dietary energy can cause excessive protein catabolism to meet energy requirements, resulting in loss of essential amino acids for other critical functions such as gamete formation. Therefore, the dietary E:P ratios of the broodstock diets could be a major determinant of spawning success and larval quality in characids.
The objective of the study was to compare the effects of
high (40%) and low (30%) protein diets containing similar amounts of total energy on reproductive performance of gamitano (Colossoma macropomum) and paco (Piaractus brachypomus) broodstock as indicated by biochemical composition of plasma, ovules, and semen. Proteins and lipids as well as essential amino and fatty acids interact metabolically, and analysis of all of these components of the tissues was desired. However, the amount of tissue obtained for analyses in this study was limited. Both diets contained at least 20% fish meal and the diets appeared to have no deficiencies in essential amino acids. Some of the highly unsaturated fatty acids (HUFAs) such as arachidonic acid (20:4n-6), eicosapentaenoic acid (20:5n-3) and docosahexaenoic acid (22:6n-3) are known to be important for reproduction in other fish species (Izquierdo et al., 2001; Sargent et al., 2002). Tissue stores of these fatty acids can be enhanced through the diet, but diets in the present study had very low levels of HUFAs . The relative proportions of lipid classes can also be manipulated through the diet to variable extents in different tissues, but baseline data is needed before the effects of dietary manipulations can be evaluated.